Cytoplasmic aggregates capable of synthesizing vaccinia virus DNA at rates approaching those obtained in intact cells will be isolated and characterized. A detailed analysis will be made of the size and properties of the newly-synthesized DNA and of the several viral and host enzymes or other factors necessary for viral DNA synthesis. The physical location of parental DNA and at least several of the required enzymes on cytoplasmic membranous structures will be an aid in isolation studies and should provide important insights into the mechanism of DNA synthesis in higher organisms, where DNA synthesis also appears to take place on membranes. Several of the strucutural proteins and related components of the outer coat and inner nucleocapsid of the poxvirus virion will be isolated and studied to determine which of these are important for (a) attachment to cells, (b) penetration, and (c) intracellular release from the phagocytic vesicle. The components will be incorporated into the lipid bilayer of artificial, phospholipid particles (liposomes) to obtain "virus-like" particles. Various nucleic acids, proteins, and chemotherapeutic agents will be incorporated into the inner, aqueous phase of the liposomes. The aim will be to design a particle which will show specificity of attachment, and upon ingestion, catalyze the lysis of the phagosome so that materials trapped in the interior of the liposomes will be released intact into the cytoplasm. Information obtained from these studied will be used to construct particles for possible use in gene therapy, enzyme replacement therapy and target- specific delivery of chemotherapeutic agents.